Elevator dispatching system



Jan. 1, 1952 w. F. EAMES ELEVATOR DISPATCHING SYSTEM 2 SHEETSSHEET lFiled Aug. 19

R D 3 R D Y 2 Fig.l.

INVENTOR Fig2.

WITNESSES: 7%

Jan. 1, 1952 w. EAMES ELEVATOR DISPATCHING SYSTEM 2 SHEETSSHEET 2 FiledAug. 19, 1950 INVENTOR William F.E es. 74/

ATT RNEY WITNESSES: 47y

Patented Jan. I, 1952 UNITED STATES PATENT OFFICE ELEVATOR DISPATCHINGSYSTEM William; F;- -Ea-mes, Westfiqld, N. .I., assignor toWestinghouse; Electric Corporation, East Pittsburgh, Pa., a corporation,of' Pennsylvania ApplicationAugust 19, 1950, Serial No. 180,400

19 Claims.

The invention relates to elevator systems in which a pluralityofcarso-perateas-a bank, and particularly to a dispatching: system for. aninstallation of suchtype for individually. dispatchlllg the cars atsuitable intervals from a' dispatching floor.

There have been many elevator dispatching systems suggested, and manyare now in :use, including .the rotational dispatcher for abank ofcars,in which the cars are'dispatched from a terminal floor in apredetermined invariable sequence, and the non-rotational dispatchenrin'which the-cars are dispatched from the terminal in the order of theirarrival.

In both of these cases the dispatching signal is given to the operatorattheexpiration of a period-of time after arrival at thedispatchingfloor depending upon estimated traffic conditions. However, for a givenbuilding tr'alfic conditions do not remain. constant throughout the day,and asa result there'may be undesirable delays in answering calls 'forservice under some conditions'becausethe dispatching schedule issuchthat-two or more cars of the bank may be at the dispatching terminal atthe same time, thereby reducing the number of cars available forservicing the intermediate floors of the building.

In another type of dispatching system designed to improve this situationwhen more than one car is present at the dispatchingterminaL thedispatching time, or interval, of the first car under steady loadconditions the cars of the sys-.

tern will become properly spaced, but with variations in loadingthere-will be an undesirable time lag in the realignment of thedispatchingschedule responsive to the resulting bunching of the cars,and the situation is worsened if thechange in loading occurs suddenly.

In accordance with the present invention a dispatching system isprovided in which the dispatching interval is'varied continuously inaccordance with thenumber of calls for service on the elevator systemand rate of I change in the number of calls for service. For example,where a bank of elevators has substantially equal up'anddown loading,which may be classed as heavy, which'tapers oil over 'a'short-periodi toa, light loading and then increases toanother period of heavy loading,the present invention will respond by first decreasing the dispatchinginterval to prevent cars 'bunching at the dispatching terminal duringthe light load period,

and then, increasing the interval again as the loading becomes heavy.The dispatching interval is kept continually in phase-with the-loaddemand as it changes, and in the event of a sudden change in the rateof'loading bya, predetermined-amount the dispatch-signal may be givensubstantially instantaneously.

It is, therefore, an object ofthe invention to providea dispatchingsystem in which the elevator cars of a bank aredispatched from atervminal, or dispatching'floor, in a period of time after arrival whichcontinuously varies in accordance with anumber of calls for'servioeregistered on the systemas-well as the rate of change in the number ofsuch registrations.

It isafurther object of the invention toprovide-an elevator dispatcherwhich is responsive to..the registered car calls'and/orhall calls tocontinuously vary the-dispatching interval in accordance Wi-thvariations in the number of calls enhelev tor syst m.

- Other; objects of theinvention-willbe apparent from the followingdescription andthe accompany n d awi whi h:

Figure l is a-schematic view of an elevator system illustrative of thetype-to which the inent n may-b pp i d;

Fig. 2; is a schematiccircuit in straight-line .form-of the dispatchingsystem of the invention, and

Fi 2A isa schematic key-sheet indica in the location of the relays-andcontacts'of Fig. 2-when pierced-besidev Fig. 2.

The invention, of course, -is primarily applicable to banks of two ormoreelevator cars, al-

though it may have some application to a. single car. By way-ofillustration the invention-will be-described with respect to a bank offour cars,

one of which is schematically illustrated in :Fig. 1. As indicated inthe circuit diagram, Fig. 2,

the invention may be'applied abank of four cars designated as A, B, Cand D.

Referring to Fig. 1, car-A of the bank is suspended from one or moreropes or cables 2 which .extendover a hoisting sheave 4 and'are conaconventional type having a plurality of fixed contacts i mounted ininsulated relation and Spaced in accordance with the spacin of thefloors of the building, and a movable cross-head or carriage i2 havingcontact brushes 14 mounted on it for engaging the stationary contacts H]as the cross head moves up and down the face of the selector inaccordance with car movement, as governed by threaded shaft [6 drivenfrom the motor 6 through suitable reduction gearing l8. A contact A28]is also on the selector at a position corresponding to the top terminalof the elevator shaft to be engaged by brush A22 when the car reachesthat position. Similarly, contactAZl corresponds to the lower terminal,the position of the carriage 12 as shown corresponds to the car being atbasement level.

The motor 6 may be controlled in any of a number of ways which areconventional, such as by a car switch CS to be manipulated by theoperator in the car to start the car, and the car may be stoppedautomatically by car buttons CB mounted in the car, and push-buttonstations HR in the hall or corridor at each floor. Usually, of course,there is one car button corresponding to each floor of the building, andat each-intermediate fioor the push-button stations HB comprise an upbutton and a down button. The automatic stopping of the car in responseto these buttons is so well known that a detailed description thereof isnot considered necessary. Of course, the system may be such that thestopping is controlled manually by the car switch CS in response tosignals to the operator effected by the push-buttons. The carbuttonsupon being pressed will remain in circuit-closing position until the carstops at the designated floor or until the car completes its trip in agiven direction, and the hall buttons upon being pressed energize callregistering relays which remain in energized or contact-closed conditionuntil the call is answered by the car.

The above-described apparatus for car A is duplicated for cars B, C andD, it being understood, of course, that for the group or bank of cars,only one set of hall buttons H at each fioor is required becausecross-connections between the floor selectors of the four cars insurethat the nearest car moving in the desired direction of travel willanswer and cancel the hall call, in accordance with usual practice.

Referring to Fig. 2, the dispatching timer of the invention includes avariable speed motor M, the armature 3d of which is connected in a loopcircuit with the armature 32 of a generator G which is driven by aconstant speed alternating current motor 34. The motor M is providedwith a separately energized field MF. The generator G is provided with ashunt field winding GF, the degree of excitation of which determines theoutput of the generator, and, accordingly, the speed of the timing motor30. This is usually termed a variable-voltage or Ward-Leonard type ofmotor control system.

The generator G is mechanically connected through an electromagneticclutch AC to a cam it which sequentially closes a plurality of pairs ofcontacts RA, RB, RC and RD. Suitable gearing 6i may be interposedbetween the clutch and cam to provide a desired rate of rotation of thecam.

The timing motor M is connected through a second electromagnetic clutchSC to timing cams 52 and A l for a purpose to be described.

In the dispatching sequencea car upon selection as the next car to leavereceives a next" light ANL and after a time interval a start light ASL.These are shown in Fig. 1 as mounted in the car to indicate to theoperator that his car is next and he can begin to receive passengers.Preferably a hall lantern AHL is lit at this time to signal to intendingpassengers that the car is available. When the operator receives thestarting signal ASL he may proceed on his trip.

For the purposes of this description the dispatching floor will beconsidered to be the upper terminal, and the dispatching interval willbe controlled by car and hall calls for service in the down direction.

If car A is the first to arrive adjacent to the terminal, and assumingthat a car has just left the terminal as car A arrives, floor selectorcontacts A22 and A20 engage and relay AU will be energized (Fig. 2) andwill remain energized so long as car A is at the terminal. With relay AUenergized, contacts AUl close which completes a circuit through thewinding of clutch AC and the series of break contacts ANI through DNIthereby engaging the clutch AC and rotating selector cam 40,,whosepurpose is to select the next car to leave in the event that two or morecars should be at the dispatching floor at the same time.

Contacts AUZ also close preparing a circuit for next relay AN throughbreak contacts ASZ and open contacts RA of the switch operated by cam40. A circuit is also prepared for the start relay AS which isincomplete at this time by reason of the open contacts ANZ and ST3.

As the cam 40 advances, with a relatively rapid rotation which may beassumed to be one revolution per second, contactor RA will be closed andthereby complete the circuit to relay AN. The energization of relay ANopens contacts ANI in the circuit of the winding of clutch AC, therebystopping cam 4% It also closes contacts AN3 in circuit with the nextlight ANL and the hall lantern AHL for car A, and it closes contacts ANZin the circuit of start relay AS.

With the winding of clutch SC energized through break contacts ST! andthe series of break contacts ASI through DSi, cam switch S will beclosed in a predetermined time depending upon the speed of the timingmotor 30. With the closure of contacts of cam switch S, relay ST isenergized. The relay picks up and establishes a holding circuit foritself through contacts STZ. At the same time break contacts STl openand deenergize the clutch SC, permitting the cam 41. to return to itsstarting position under the influence of spring 43.

Relay ST upon energization closes its contacts ST3 thereby completingthe circuit to relay coil AS, the circuit comprising Relay AS closes itscontacts ASA to energize the start signal ASL. It also closes contactsASS which establish a holding circuit for itself. Contacts ASI willopen, breaking the circuit to the relay winding ST and the clutchwinding SC. Contacts ASA, in addition to energizing the start signalASL, may also be effective to control a circuit for starting the car, asindicated, in the event that the elevators are of the automaticpushbutton type.

As the car leaves the terminal in response to the starting signal, theengagement of the floor selector contacts A20 and A22 is broken and thesystem is ready to respond to the next car at the terminal,assuming-that-cars B, Cor D arrived 1 duringtheabovedescribed-dispatching sequence for car A.-In-thatcase'selectorcontacts B- B22, or C20-C22,-or D20-D22will be inengagementand the respective relays BU, CU or DU will pick up andtheabove described next and start sequence will be repeated.

1 Of course, while car A is waiting for-its start signal after receivingits next signal, the arrival-of-subsequent cars do not affectthedispatch operation-of car A because even though the relays BU, CU or DUbecome energized and close their contacts BUI, etc. the circuit throughclutch winding-AC -is broken by contacts AN! which do not reelose untilAN-is deenergized by the pickup of start relay AS of car A which opensits contacts A52.

Assuming further that there are no cars at-the terminal, that is, noneof the relays AU through -DU are energized, the winding of clutch SC isenergized (ST! beingclosed) and upon rotation of cam 42 switch S willclose. Relay ST will then be energized and hold-in through its contactsSTZ. Clutch winding SC will be deenergized by the opening of ST! andcam- 42 will be returned to its'starting position by spring 43. Thecontacts ST3 in the circuit of start relays AS to DS will close, so thatuponthe arrival of the next car,

that field winding GB of generator has been energized to any requireddegree for operating the timing-motor M. Howeversuch energization inaccordance with the invention will be varied in proportion tothe numberof calls for service on the system, and the rate of registration of said7 calls.

For example, in Fig. 2 the field winding GF may be energized throughfour parallel resistance circuits a, b, c and d corresponding tothe fourcars A, B, C and D. Each resistancecircuit is divided into equalsections corresponding to the number of floors to be served inresponseto the car buttons CB, andthe floors to be served in response to down.hall buttons at the floors. Assuming a building of twenty floors, therewill be twenty resistor sections corresponding to the number of carbuttons and nineteen sections corresponding to the number of down hallbuttons. The resistor sections are normally shunted, when there are nocalls on the system, by break contacts to be operated by the car buttonsICB through 20GB, and break contacts 2DR through IBDR on the down callregistering relays (not shown) which operate in response to the downhall buttons, and are held in. operated condition until a car answersthe call.

.A fixed resistor is in series with each of theresistance circuits a, b,c and d to provide a desired minimum value, and contacts 52 are providedin each branch and are closed when the respective cars are placed inservice. The four resistance circuits are connected in parallel througha series resistance 54 to the generator shunt field winding GF. Theresistor 54 is shunted by break contacts ID2 for a purpose describedhereinafter.

By way of example and not limitation, the fixed resistors 51) may be ofthe order of ohms, and each of the segments of the resistance circuitsa, b, c and d may be 20 ohms.

Assuming that car A isithe only car in service, if there are noregistered callson'the system, resistance a will be shunted bytheclosedcontacts of car buttons CB and. the DR contacts. of the hall callstoring relays. The. only resistance in circuit with the field windingGEwill. berepresented by fixed resistors 50 and..54. .This. will afiorda relatively high...energization, of GE and accordingly, a relativelyhighspeed. of the timer motor M. When passengers enter car A. and carbuttons are pressed indicating the desired. destination floors,corresponding sections, of resistance a are placed in the circuit of GE,and as down floor-calls are registered corresponding contacts DR willopen thereby cutting in more resistance to further decrease theenergization of GE and accordingly increasethe timer interval tocorrespond to an expected longer through-triptime of the car.

If car B is placed in -service,nclosing its contacts 52, its DR contacts.correspondingto the hall calis registered. will also open,andhcarbutton contacts corresponding tothe desires of passengersentering car B willopen. ,With the. two

' resistance paths. a and b in parallel, GEwill be energized to a higherdegree therebyincreasing the speed of motor, M and .decreasingthetimerinterval. Similarly, as cars C and'D are brought into service, theadditional resistors c andd bei come efiective, the hall calls. onthesystem being common to all the cars, and car hallsbeingefiective tomodify the resistor associated. only-with the car in which theyareregistered.

From the foregoing it is apparent that the speed of the dispatcher motorM, and hence-the length of the dispatching-interval, is a continuallyvarying quantity depending upon the number of car calls and hall callsregistered at any given instant. That is, with asteady balanced loadingof calls, an interval of 30 seconds for dispatching cars from-the topterminal may be adequate. However, if the loading decreases, therebydecreasing the round-trip time of the cars, the cars may start to bunchor accumulate at the I dispatching terminal unless the dispatch intervalis shortened. This is automatically taken care of in the present systembecause as the number of calls decrease, fewer of the DR, contacts willbe open and hence the energization of the gener-- ator field GF willincrease. The reverse is true of course for an increase of loading onthe system resulting in an increased round-trip time, making a longerdispatch interval desirable to insure a proper distribution of the cars.

Also as cars are taken out of service, or brought into service, openingor closing the respective contacts 52, the dispatch interval will.automatically varyto adapt the cars in .service to the loading on thesystem at that time.

At the lower part of Fig. 2 is shown a circuit which is responsive tothe rate of change inthe registration of calls, in this casedownhall-calls for example, including a capacitor 63, relays ED and 2D,sectionalized resistors. 62 and Y64, and fixed resistors .65 and 68.

The capacitor 60, which may he of the order of 300 or 400 microfaradscapacity, is connected in series with the windings of relays ID and 2Din a circuit connected between the junction of resistors 52-66 and64-B8.

The segments or resistor 62 are provided with shunts including thenormally open contacts ZDRl through iliDRi of down call registeringrelays (not shown) which are operated in response to the registration ofcalls for service at the second through tenth floors.

Similarly, the segments of resistor 64 are shunted by circuits includingthe normally open contacts IIDRI through IBDRI corresponding to the callstoring relays for the eleventh through nineteenth floors.

The relays ID and 2D are of the instrumenttype operating upon a fractionof a watt, and are polarized so that they are responsive to thedirection of current flow through their windings. Relay ID is set tooperate at a lower current than 2D.

Relay ID in operation closes its contacts ID! in a circuit which shuntsthe resistance circuits a, b, c and d, and open its contacts [D2 whichare in shunt circuit for the resistor 54 in series with the generatorfield winding GF. Relay 2D upon energization closes its contacts ZDIwhich are in circuit with contactor S controlled by the cam wheel 44 ofthe timer.

Assuming that there are no calls on the system and the contacts ZDRIthrough IQDRI are open as shown, the condenser 60 will be charged fromLI, resistor 68, condenser 60, relay windings ID and 2D, resistor 66 andL2, because the total resistance of the sectionalized resistors issubstantially larger than that of the fixed resistors 66 and 68. Therelay side of the condenser 63 will therefore be charged negatively, andno current will be flowing through the relay circuit because it isassumed that the condition existed long enough to have charged thecondenser.

As down-calls are registered, corresponding segments of the resistors 62and 64 will be shunted by the DRI contacts, thereby decreasing the totalvalues of these resistors. If we assume an extreme case, by way ofexample, where suddenly from a period of no down-calls on a system thereare suddently registered fifteen down-calls, the values of resistances62 and 64 will decrease to a point where the current through thecondenser will reverse in direction, namely from LI through the fewremaining segments of resistor 62, the relay windings 2D, ID andcondenser 50 through the remaining segments of resistor 64 to L2.

Under this extreme condition, there would be sufiicient current flowingthrough the directional relay windings ID and 2D to operate both ofthem. The complete charging of the condenser 60 will of course bedelayed in accordance with the resistance remaining in the circuit.

The operation of ID, closing IDI, speeds up the dispatcher timer byincreasing the energization of shunt field GP to dispatch a car from theterminal sooner than the car otherwise would be dispatched. At thispoint the normally closed contacts IDZ do not open.

The operation of relay 2D closes ZDI to energize relay ST to give astart signal immediately to a car at the terminal provided that aminimum interval has elapsed since the last start signal has been given,which is determined by contact S operated by cam wheel 44. That is,

' if a car is present at the top terminal, it will receive an immediatedispatch signal assuming that S is closed, but if no car is there, thesignal will be stored until a, car does arrive because relay ST willremain energized through its holding contacts STZ and upon the arrivalof the car the car will immediately receive its "next and start signals.

In the operation just described the operation of relay ID is of no greatconsequence because of the simultaneous operation of relay 2D. However,if there are a smaller number of down calls, than the fifteen assumedabove, there will be a smaller current flow through the relays ID and 2Dwhich may not be sufficient to operate relay 2D, and an immediate startsignal will therefore not be available. However, there may be sufiicientcurrent to operate the more sensitive relay ID for a time, and speed upthe dispatcher by closing contacts IDI which shunt the resistor circuitsa, b, c and d. Therefore, a smaller increase in down hall-calls causingsuflicient current to flow to operate relay ID only, will effect aspeeding up of the dispatcher signal which will move cars from the upperterminal more rapidly to take care of the increase in down calls.

When the increase of down calls is satisfied, resulting in many or mostof the DRI contacts opening, the current through the condenser willagain reverse, making the relay side negative, causing a reversal in thecurrent flow through the relay coils. The reversal will have no effectupon relay D2 but it will cause relay DI to open contacts IDZ, and willleave contacts IDI normally open. The normally closed contacts ID2, whenopen, remove the shunt around resistor 54 in series with the field GFwhich will lengthen the dispatching interval.

If desired, this contact ID2 may be employed to speed up the dispatcherat the opposite terminal to decrease the dispatching interval at thatpoint and thereby speed the dispatch of cars in the up direction. Thatis, although the foregoing description has been specific to dispatchingfrom the top terminal in connection with "down calls for service, it maybe desirable to have a bottom floor dispatcher in connection with upcalls. Such an up dispatcher would be substantially in accordance withFig. 2 except that segmental resistors a, b, c and (1 would becontrolled by contacts on the call registering relays DU which arecontrolled by the up corridor push buttons.

On the other hand, the requirements of a given installation may renderit more expedient to dispatch from the bottom floor only, omitting thetop floor dispatcher.

Further, it may be expedient to control either or both top and bottomdispatchers in accordance with car button calls only, in a situationwhere up or down corridor calls are infrequent, or if most of thepassengers collected in response to corridor calls normally desire toproceed to one terminal or the other, the dispatcher may be controlledentirely by the number and rate of registration of corridor calls.

Quite obviously many aspects and modifications of the system disclosedwill present themselves and it is intended that the invention be limitedonly by spirit and scope of the appended claims.

I claim as my invention:

1. In an elevator system including a bank of cars for serving aplurality of floors and provided with means for registering calls forservice for said floors; means for individually dispatching said carsfrom one of said floors at periodic intervals including a timing deviceand means controlled thereby for giving dispatch signal to said cars,and means for varying the operation of said timing device to vary theinterval between dispatch signals in accordance with the number ofregistered calls for service on said system and the rate of registrationof said calls.

2. In an elevator system including a bank of cars for serving aplurality of floors and provided with means for registering calls forservice for said floors; means for individually dispatching saidcars'irom ione'of said floors at periodic intervals including a timingdevice and means controlled thereby for-giving a dispatch signal to saidcars, and means for varyingthe operation of said timingdevice'to varythe interval between dispatch signalsin accordance with the number ofregistered calls for service on said system, and means forfurthervarying the operation of said timing device in response to a rateof registration of said calls above a predetermined amount fordecreasing the interval as determined by said last named means.

3. In an elevator system including a bank of carsfor serving a pluralityof floors" and provided with means for registering calls forservice forsaid floors; means'for individually dispatching said cars from one ofsaid floors at periodic intervals including a timing device and meanscontrolled thereby for giving a-dispatch signal to said cars, andmeans'fo'r varying the-operation of said timing device to vary theinterval between dispatch signals in accordance with'th'e number ofregistered calls for service on said system, and means responsive to arate of registration of said calls above a predetermined amount forgiving a dispatch signal substantially instantaneously.

4. In an elevator system including a plurality of cars servingaplurality-of floors and means-for registering callsfor service by thecars with respect to the floors, one of said floors being a dispatchingfloor, means forsequentially dispatch ing the cars from the dispatchingfloor at con-' tinuously variable-intervals comprising a variable speedvoltage responsive timing device, and means for energizing it at avariable voltage continuously proportional in magnitude to the number ofregistered calls for service on said system.

5. In an elevator system including a plurality ofcars serving aplurality of'floors and means for registering calls for service by thecars with respect to the floors, one of said floors being a dispatchingfloor, means for sequentially dispatching the cars from the dispatchingfloor at continuously variable intervals comprising a variable speedelectric timing motor, an electric generator having its armatureconnected in a loop circuit with the armature of said motor and aseparately excited shunt field winding, means for exciting said windingincluding means for varying the excitation thereof in accordance withthe number of registered callson said system.

6. In an elevator system including a plurality of cars serving aplurality of floors and means for registering calls for service by thecars with respect to the floors, one of said floors being a dispatchingfloor, means for sequentially dispatching the cars from the dispatchingfloor with a continuously variable time delay comprising a variablespeed electric timing motor, an electric generator having its armatureconnected in a loop circuit 'With the armature of said motor and aseparately excited shunt field winding, means for exciting said windingcomprising means for varying the excitation thereof in accordance withthe number of registered calls on said system and the duration of suchcalls.

7. In an elevator system including a plurality of cars serving aplurality of floors and means for registering calls for service by thecars with respect to the floors, one of said floors being a dispatchingfloor, means for sequentially dis patching the cars from the dispatchingfloor with a continuously variable'time delay comprising a variablespeed electric timing motor, an electric generator having its armatureconnected in a loop circuit with thearmature of said motor and aseparately excited shunt field winding, means for exciting said windingcomprising means'for varying the excitation thereof in accordance withthe number of regis-teredcalls-on said system and means responsive tothe-rate of registration of such calls for further varying theenergization of said winding.

8. In an elevator system including a plurality of cars serving aplurality of floors and means for registering calls for service by thecars with respect to the floors, one of said floors being a dispatchingfloor, means for sequentially 'dispatching the cars from the dispatchingfloor witha continuously variable time delay after arrival thereof atsuch floor comprising a variable speed electric timing motor, anelectric'generator having its armature connected in a loop circuit withthe armature of said motor and a separately excited shunt field winding,means for exciting said winding comprising means for varying theexcitation thereof in accordance with the number of registered callsonsaid system and the duration of such calls and means responsive to therate of registration of such calls f0r-further varying the energizationofsaid winding.

9.-In an elevator system including a plurality of cars servinga'plural-ityof floors and call means at said floors-forregistering callsfor service in the-down direction and call means in each car for eachfloorserved thereby, means a ,for dispatching saidcars in sequence froman upper floor comprising a dispatching signal and an electric timingmotor for effecting the energization thereof, means for automaticallyand continuously var-ying the speed of such motor including a 1 constantspeed electric generator electrically'connected-thereto and having aseparately excited field winding, means for variably exciting saidwinding including a plurality of sectionalized resistors, onecorresponding-to each car, and means connecting them in parallel circuitrelation with each other and'all in'series circuit relation with saidwinding and a source ofvol'tage, separate shunt cicrcuits for thesections of said-resistor each including a normally closed contact, suchcontacts to be opened in response to the operation of said callregistering means -to-vary the resistance of the circuit of saidwinding. 7

10. In an elevator installation including a bank of cars serving aplurality of floors and means at each of said floors for registering acall for service by the-cars for that floor; a system for dispatchingsaidcars from one of said floors including: means for selectinga car atthat floor to be the next to be dispatched, a dispatch signal,-andmeansiorenergizing said signal for the car so selected after a time intervalor variable duration depending upon the number of unanswered registeredcallsfor service on thebank of cars.

11. In an elevator system in which a plurality of cars are sequentiallydispatched from one floor to serve a plurality of other floors and inwhich means are provided for registering calls for service to saidfloors by said cars, means at said one floor for giving periodicdispatch signals, means for continuously varying the period betweendispatching signals in accordance with the number of registered callsfor service on said system, and means for further varying such period inrell sponse to the rate of change in the number of calls registered.

12. In an elevator system in which a plurality of cars are sequentiallydispatched from one floor to serve a plurality of other floors and inwhich means are provided for registering calls for service to saidfloors by said cars, means at said one floor for giving periodicdispatch signals, means for continuously varying the period betweendispatching signals comprising a voltage responsive timing device, asource of variable voltage therefor, and age of said source inaccordance with the number of registered calls for service on theelevator system.

13. In an elevator system in which a plurality of cars are sequentiallydispatched from one floor to serve a plurality of other floors and inwhich means are provided for registering calls for service to saidfloors by said cars, means at said one floor for giving periodicdispatch signals, means for continuously varying the period betweendispatching signals in accordance with the number of registered callsfor service on said system, and means for further varying such period inresponse to the rate of change in the number of calls registered, andadditional means responsive to the rate of registration of said callsfor further varying the voltage of said source.

14. In an elevator system in which a plurality of cars serve a pluralityof floors and which are provided with means responsive to calls forservice registered by push-buttons at said floors and push-buttons ineach car corresponding to the floors served thereby; means fordispatching said cars sequentially from one of said floors comprisingselecting means for determining the next car to be dispatched, adispatching signal and means operable with a time delay for energizingsaid signal for a car so selected, said last named means includingtiming mechanism and means for varying continuously the timing operationthereof in accordance with the number of calls for service registered onthe elevator system by said push-buttons.

15. In an elevator system including a plurality of cars serving aplurality of floors and which are provided with means responsive tocalls for service registered by switches at said floors and switches ineach car corresponding to the floors served thereby, means fordispatching said cars sequentially from one of said floors comprisingselecting means for determining the next car to be dispatched therefrom,a dispatch signal and means operable with a time delay for energizingsaid signal for a car so selected, said last named means including avariable speed electric timing motor, a variable-voltage generator forenergizing said motor, and means for exciting said generator with avoltage continuously variable in magnitude in proportion to the numberand duration of calls registered by said push-buttons in said cars.

16. In an elevator system including a plurality means for continuouslyvarying the volt- I 12 of cars serving a plurality of floors and callregistering means at each floor for registering calls for service in onedirection of travel with re spect to a dispatching floor, and means forsequentially dispatching said cars from said floor including a dispatchsignal in each car, a variable speed timing device and a contactoroperated thereby for energizing said signals, means for varying thespeed of said timing device in accordance with the number and durationof calls registered, and means responsive to an increase in the rate ofregistration of said calls above a predetermined amount for increasingthe speed of said timing motor, and means responsive to a furtherincrease in the rate of registration for energizing the dispatchingsignal for a car at the dispatching floor substantially instantaneously.

17. In an elevator system including a plurality of cars serving aplurality of floors and call registering means in each car'forregistering calls for service in the direction of travel of the cartoward a dispatching floor, and dispatching means at such floor fordispatching cars therefrom in sequential intervals including a timingdevice, and means for varying continuously the operation of said devicein accordance with the number of calls registered on said callregistering means. i

18. In an elevator system including a plurality of cars serving aplurality of floors and call registering means at each floor forregistering calls for service by such cars and means for sequentiallydispatching said cars from one of said floors including a dispatchsignal for each car, a variable speed timing device and contactoroperated thereby for energizing said signals, means for varying thespeed of said timing device in accordance with the number and durationof calls registered, and means responsive to the rate at which saidcalls are registered to increase or decrease the speed of said timingmotor as such rate of registration increases or decreases a predetermined amount.

19. In an elevator system in which a plurality of cars serve a pluralityof floors and which are individually provided with stopping meansresponsive to calls for service registered by pushbuttons at said floorsand push-buttons in each car corresponding to the floors served thereby,means for dispatching said cars sequentially from one of said floorscomprising selecting means for determining the next car to bedispatched, a starting signal and means operable with a time delay forenergizing said signal, said last named means including a variable speedelectric timing motor, a variable-voltage generator for energizing saidmotor, and means for exciting said generator with a voltage continuouslyvariable in magnitude in accordance with the number and duration ofcalls for service registered by said push-buttons at said floors.

WILLIAM F. EAMES.

No references cited.

